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False positive in the measurement of thyroglobulin induced by rheumatoid factor. 2015

G Astarita, and S Gutiérrez, and N Kogovsek, and E Mormandi, and P Otero, and C Calabrese, and G Alcaraz, and A Vázquez, and M Abalovich
Endocrinology Division, Durand Hospital, Buenos Aires, Argentina.. Electronic address: gbastarita@intramed.net.ar.

BACKGROUND We report a case of interference in thyroglobulin (Tg) measurement in a woman with differentiated thyroid cancer and rheumatoid arthritis history. Due to discordant Tg in relation to TSH concentrations and negative images, we investigated possible interference in the measurement of Tg. METHODS During the follow-up we measured Tg by chemiluminescence (TgQL) using Immulite 2000 immunoassay system. To investigate possible interference in Tg measurement, we made serial dilutions, re-testing of Tg by an alternative method: electrochemiluminescence, Cobas 6000 analyzer (TgEQL), recovery test of Tg and polyethylene glycol (PEG) 6000 precipitation. RESULTS During the patient follow-up, the TgQL ranged between <0.3 and 16.1ng/ml. In the evaluated serum samples very high titers of rheumatoid factor (RF) were found. When RF titers were lowered post PEG precipitation, Tg QL concentrations became undetectable. CONCLUSIONS We describe an unusual case of interference in Tg assay due to RF. When disagreement among Tg concentrations, images and clinical features is observed, we suggest taking into account the evaluation of possible Tg interference to avoid unnecessary complementary exams and inappropriate treatment.

UI MeSH Term Description Entries
D007118 Immunoassay A technique using antibodies for identifying or quantifying a substance. Usually the substance being studied serves as antigen both in antibody production and in measurement of antibody by the test substance. Immunochromatographic Assay,Assay, Immunochromatographic,Assays, Immunochromatographic,Immunoassays,Immunochromatographic Assays
D008163 Luminescent Measurements Techniques used for determining the values of photometric parameters of light resulting from LUMINESCENCE. Bioluminescence Measurements,Bioluminescent Assays,Bioluminescent Measurements,Chemiluminescence Measurements,Chemiluminescent Assays,Chemiluminescent Measurements,Chemoluminescence Measurements,Luminescence Measurements,Luminescent Assays,Luminescent Techniques,Phosphorescence Measurements,Phosphorescent Assays,Phosphorescent Measurements,Assay, Bioluminescent,Assay, Chemiluminescent,Assay, Luminescent,Assay, Phosphorescent,Assays, Bioluminescent,Assays, Chemiluminescent,Assays, Luminescent,Assays, Phosphorescent,Bioluminescence Measurement,Bioluminescent Assay,Bioluminescent Measurement,Chemiluminescence Measurement,Chemiluminescent Assay,Chemiluminescent Measurement,Chemoluminescence Measurement,Luminescence Measurement,Luminescent Assay,Luminescent Measurement,Luminescent Technique,Measurement, Bioluminescence,Measurement, Bioluminescent,Measurement, Chemiluminescence,Measurement, Chemiluminescent,Measurement, Chemoluminescence,Measurement, Luminescence,Measurement, Luminescent,Measurement, Phosphorescence,Measurement, Phosphorescent,Measurements, Bioluminescence,Measurements, Bioluminescent,Measurements, Chemiluminescence,Measurements, Chemiluminescent,Measurements, Chemoluminescence,Measurements, Luminescence,Measurements, Luminescent,Measurements, Phosphorescence,Measurements, Phosphorescent,Phosphorescence Measurement,Phosphorescent Assay,Phosphorescent Measurement,Technique, Luminescent,Techniques, Luminescent
D001774 Blood Chemical Analysis An examination of chemicals in the blood. Analysis, Blood Chemical,Chemical Analysis, Blood,Analyses, Blood Chemical,Blood Chemical Analyses,Chemical Analyses, Blood
D005189 False Positive Reactions Positive test results in subjects who do not possess the attribute for which the test is conducted. The labeling of healthy persons as diseased when screening in the detection of disease. (Last, A Dictionary of Epidemiology, 2d ed) False Positive Reaction,Positive Reaction, False,Positive Reactions, False,Reaction, False Positive,Reactions, False Positive
D005260 Female Females
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults
D012217 Rheumatoid Factor Autoantibodies found in adult RHEUMATOID ARTHRITIS patients that are directed against GAMMA-CHAIN IMMUNOGLOBULINS. Factor, Rheumatoid
D013954 Thyroglobulin
D013964 Thyroid Neoplasms Tumors or cancer of the THYROID GLAND. Cancer of Thyroid,Thyroid Cancer,Cancer of the Thyroid,Neoplasms, Thyroid,Thyroid Adenoma,Thyroid Carcinoma,Adenoma, Thyroid,Adenomas, Thyroid,Cancer, Thyroid,Cancers, Thyroid,Carcinoma, Thyroid,Carcinomas, Thyroid,Neoplasm, Thyroid,Thyroid Adenomas,Thyroid Cancers,Thyroid Carcinomas,Thyroid Neoplasm

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